The present invention relates generally to improvements in the operation of data channels, and more particularly to calibrating data channels more effectively to compensate for thermal fluctuations in transducers such as read/write heads.
High performance data handling systems frequently make use of delicate transducers. In many wireless communications, for example, antennas and sensors must be exposed directly to the air. This can cause temperature fluctuations that will disrupt their calibration and can degrade or even prevent their performance.
Modern disc drives position transducers adjacent to a spinning disc, the close positioning required for reading the weak signals received from the closely spaced tracks. Disc drives are the primary devices employed for mass storage of computer programs and data. The advantages of disc drive technology over other means of data storage include a lower cost per unit of storage capacity and a generally higher transfer rate.
In a typical xe2x80x9cWinchesterxe2x80x9d magnetic disc drive, digital data is written to and read from a thin layer of magnetized material on a surface of one or more discs. A load beam supports a hydrodynamic air bearing slider close to each data surface of a rotating magnetic disc. The load beam supplies a downward force that counteracts the hydrodynamic lifting force developed by the slider""s air bearing. The slider carries a magnetic transducer for communication with individual bit positions on the rotating magnetic disc. Even a small thermal variation resulting from ambient temperature shifts can disrupt the magnetic properties and physical positioning of a transducer head. Also, moving disc surfaces contact the tiny disc drive heads, frequently causing localized temperature changes in their sensitive read or write transducers.
Disc drives including thermal calibration have existed for several years. For example, U.S. Pat. No. 5,005,089 entitled xe2x80x9cHIGH PERFORMANCE, HIGH CAPACITY MICRO-WINCHESTER DISK DRlVExe2x80x9d issued Apr. 2, 1991 to Thanos et al. discloses a disc drive with a temperature sensor that is periodically checked to facilitate recalibration. Unfortunately, systems relying on periodic calibration have inherent weaknesses. Such systems respond poorly to thermal changes that occur soon after a calibration, for example. In a typical system, thermal calibration is performed every ten minutes. Reducing this interval would improve performance, but is somewhat impractical because of the processing demands it would impose.
A need therefore exists in the art for data handling systems with a more responsive thermal calibration. It is desirable that this be achieved, moreover, without a substantial increase in processing overhead. The present invention solves these problems and offers other advantages over the prior art.
The present invention differs from prior systems because it obtains and uses temperature readings aperiodically, on demand. Rather than merely obtaining temperature readings on each expiration of a fixed timer, systems of the present invention update one or more operating parameters in response to a fault detected in the data path. Data handling systems of the present invention each include at least one data path having a thermal range within which it operates best. Applicant notes that some xe2x80x9ckeyxe2x80x9d operating parameters typically have a substantial effect on this thermal range. (As used herein, a xe2x80x9csubstantialxe2x80x9d effect on a range is one that can potentially cause a shift of at least 10xc2x0 C. in either the maximum or the minimum of the range.) Temperature sensors positioned near the transducers provide a temperature reading to control circuits, which update xe2x80x9ckeyxe2x80x9d operating parameter values in response to indications of faults in a primary data path.
Systems of the present invention respond to temperature shifts, reducing the need for more frequent temperature monitoring and calculation-intensive recalibration. Other features and advantages of various embodiments will become apparent upon a review of the following figures and the accompanying explanations.